I'm going to attempt to speak on Larian's behalf here, so just bear in mind this is my interpretation.
The existing system has 3 stats for 3 styles of combat
Strength -> Melee
Dexterity -> Ranged
Intelligence -> Magic
plus 3 stats of "Nice to have" for every class.
So while you could roll to hit into Dexterity or perceive stats into Perception the splits exist so every style of combat has its basic damage and some out of combat perk, but no more. The kickstarter post specifically states that this is not based on pure realism but an attempt to make balanced stats.
I myself would further posit it's an attempt at balancing between simulationists, role players and strategy gamers. Role players can't make every kind of class they'd like to imagine but there's some room to make the clever archer or the average strength warrior that isn't <i>too</i> weak. The stats fit into a broadly realistic frame for simulationists and strategy gamers might not have something exactly tuned towards providing interesting options but they can make varying archetypes with the stats available.
As a result it's not wildly exciting, but it gets the job done. I'd personally like to see Strength, Intelligence and Dexterity get more widespread appeal so as to both enable roleplayers to build that Dextrous melee build without feeling too weak and also to let me make a character that blends missile and melee effectively.
The only thing I'm genuinely concerned about is that it might be hard to do without ever increasing amounts of perception and speed, otherwise your characters will hit too rarely and be hit too often. That's fine except it's odd if all effective high level characters are running faster than horses and doesn't allow for the specialness of a party of high movement hit and run specialists. I'm fine with the latter, but it does undermine the purpose of having a speed stat at all.
